1. Field of the Invention
The present invention relates to a process kit detachably used in a main apparatus such as an image forming apparatus. The present invention relates also to an image forming apparatus employing such process kit. The process kit is formed to contain only an image bearing member or a part or all of an image forming means such as a corona discharger, developing device etc. united together into a unit for an image forming apparatus.
2. Description of the Prior Art
An example of the image forming apparatus to which the present invention relates is an electrocopying apparatus. In extended use of a conventional electrocopying apparatus there is required periodical maintenance service. This service includes many works such as exchange of the image bearing member, that is, a photosensitive medium, supply of developing agent, discharge of wasted toner, cleaning of charged lines, exchange of various consumables and adjustment of the machine. Conventionally these works have been done by an expert service man. In case of large to middle size copying machines there is no difficulty related to such service by expert service men because of the limited number of the machines in market. However, in case of small size copying apparatus, in particular, in the case of the copying apparatus for private use, the number of those machines in market is very large at present. In addition, there is a great difference in the state of use among these copying machines. Therefore, it is expected that in the near future such maintenance service by the service man as mentioned above will become practically impossible to do.
Under the situation, it is very important to render unnecessary the periodical maintenance service by experts in particular for private copying machines of small size.
An idea to solve the problem is that the photosensitive drum and some other members related to the process such as developing device, cleaning device and chargers are united together into an easily exchangeable unit (hereinafter such unit is referred to as process kit). If such process kit is realized, then all of the items of maintenance work which have conventionally been done individually such as exchange of photosensitive drum, supply of consumed developing agent, discharge of wasted toner, cleaning of charged lines and, if necessary, also of developing device contaminated by toner particles etc. will be done all at once in good time when the useful life of the photosensitive drum is over. Exchange of the process kit can be carried out in simple manner by the user himself without any aid of expert service man.
This process kit has another advantage in that many kinds of such process kits may be prepared which have different development characteristics and image reproducibility and among which the user can select a most suitable one for the purpose for which the copying machine is used. In this case, a process kit now in use may be replaced by another process kit according to the purpose of copy even before the useful life of the present process unit is over. Therefore, the frequency of process kit exchange will become relatively high.
Since exchange and supply of consumables in a copying machine, hitherto, have been carried by the service man, the conventional image forming apparatus has been formed to include a counter or the like provided on the main body of the apparatus to know the state of use of the apparatus. However, if such process kits described above are used in the same apparatus while exchanging one for another many times by the user himself, then there will arise a problem in correctly knowing the state of use of every kit. For example, it is difficult to correctly know the number of times of executed image formation employing a process kit by means of the counter provided on the main body side. Therefore, there may occur a case wherein unexpectedly the service life of some consumable members of the process kit comes to an end or the toner or other consumable materials are consumed so that the user can not have sufficient time to prepare a new process kit. In such case, the main apparatus must remain unused until the new process kit is prepared. This means a loss of time.